Thursday, 19 February 2009

We share more in common with mice than a penchant for cheese, we also like the same kinds of smells. This suggests that our nasal preferences, even for biologically insignificant smells, are somewhat hard-wired or predetermined, and not entirely learned.

Nathalie Mandairon and colleagues asked thirty participants to rate their preference for a range of odours including geraniol, which has a floral smell, and guaiacol, which has a smoky whiff about it. The odours that the participants said they favoured, such as geraniol, tended to be the same ones that thirty mice spent the most amount of time sniffing, whereas the odours the humans liked least, such as guaiacol, tended to be the ones the mice were least interested in.

Importantly, the smells used in the study were varied and had no apparent biological significance. For example, it wasn't just the case that humans and mice both disliked smells that signalled rotten food or that signalled danger.

"Even if pleasantness is the result of culture, life experience and learning," the researchers said, "the present interspecies comparison shows that there is an initial part of the percept which is innate and engraved in the odourant structure."

Just what it is about the chemical structure of some substances that makes them smell pleasant to mice and humans remains to be discovered. "Taken as a whole, these results substantially affect our view of olfactory [smell-based] hedonic perception and open up new avenues for the understanding of its neural mechanisms," the researchers concluded. "They also suggest that odour exploration behaviour in mice may be used to predict human olfactory preferences."
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